runtime: implement some soft-float routines (used by GOMIPS=softfloat)

Updates #18162

Change-Id: Iee854f48b2d1432955fdb462f2073ebbe76c34f8
Reviewed-on: https://go-review.googlesource.com/37957
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/runtime/softfloat64.go

@@ -483,3 +483,115 @@ again2:
 
 	return q1*b + q0, (un21*b + un0 - q0*v) >> s
 }
+
+func fadd32(x, y uint32) uint32 {
+	return f64to32(fadd64(f32to64(x), f32to64(y)))
+}
+
+func fmul32(x, y uint32) uint32 {
+	return f64to32(fmul64(f32to64(x), f32to64(y)))
+}
+
+func fdiv32(x, y uint32) uint32 {
+	return f64to32(fdiv64(f32to64(x), f32to64(y)))
+}
+
+func feq32(x, y uint32) bool {
+	cmp, nan := fcmp64(f32to64(x), f32to64(y))
+	return cmp == 0 && !nan
+}
+
+func fgt32(x, y uint32) bool {
+	cmp, nan := fcmp64(f32to64(x), f32to64(y))
+	return cmp >= 1 && !nan
+}
+
+func fge32(x, y uint32) bool {
+	cmp, nan := fcmp64(f32to64(x), f32to64(y))
+	return cmp >= 0 && !nan
+}
+
+func feq64(x, y uint64) bool {
+	cmp, nan := fcmp64(x, y)
+	return cmp == 0 && !nan
+}
+
+func fgt64(x, y uint64) bool {
+	cmp, nan := fcmp64(x, y)
+	return cmp >= 1 && !nan
+}
+
+func fge64(x, y uint64) bool {
+	cmp, nan := fcmp64(x, y)
+	return cmp >= 0 && !nan
+}
+
+func fint32to32(x int32) uint32 {
+	return f64to32(fintto64(int64(x)))
+}
+
+func fint32to64(x int32) uint64 {
+	return fintto64(int64(x))
+}
+
+func fint64to32(x int64) uint32 {
+	return f64to32(fintto64(x))
+}
+
+func fint64to64(x int64) uint64 {
+	return fintto64(x)
+}
+
+func f32toint32(x uint32) int32 {
+	val, _ := f64toint(f32to64(x))
+	return int32(val)
+}
+
+func f32toint64(x uint32) int64 {
+	val, _ := f64toint(f32to64(x))
+	return val
+}
+
+func f64toint32(x uint64) int32 {
+	val, _ := f64toint(x)
+	return int32(val)
+}
+
+func f64toint64(x uint64) int64 {
+	val, _ := f64toint(x)
+	return val
+}
+
+func f64touint64(x float64) uint64 {
+	if x < float64(1<<63) {
+		return uint64(int64(x))
+	}
+	y := x - float64(1<<63)
+	z := uint64(int64(y))
+	return z | (1 << 63)
+}
+
+func f32touint64(x float32) uint64 {
+	if x < float32(1<<63) {
+		return uint64(int64(x))
+	}
+	y := x - float32(1<<63)
+	z := uint64(int64(y))
+	return z | (1 << 63)
+}
+
+func fuint64to64(x uint64) float64 {
+	if int64(x) >= 0 {
+		return float64(int64(x))
+	}
+	// See ../cmd/compile/internal/gc/ssa.go:uint64Tofloat
+	y := x & 1
+	z := x >> 1
+	z = z | y
+	r := float64(int64(z))
+	return r + r
+}
+
+func fuint64to32(x uint64) float32 {
+	return float32(fuint64to64(x))
+}